This invention relates to a content tobacco amount controlling device for a cigarette making machine, and more particularly to a content tobacco amount controlling device for maintaining amounts of content tobacco constant to assure desired average and uniform amounts of content tobacco.
It is very important for cigarette producers to reduce costs of cigarettes to be produced in order to increase the profits to be obtained therefrom, and great efforts have been made to attain this.
One of solutions to reduce production costs is to improved the productivity of a cigarette making machine, and at present, cigarette making machines which can produce up to 8,000 cigarettes per minute are being put to practical use.
Another solution to reduce production costs is to reduce variations of weight of content tobacco in individual cigarettes to be produced.
In particular, since the price of leaf tobacco has made a sudden rise lately, if only a small amount of content tobacco can be reduced from each cigarette, a vast amount of profit can be yielded thereby. However, if content tobacco is reduced by too large an amount, cigarettes to be produced cannot preserve predetermined quality. Accordingly, variations of weight of content tobacco of cigarettes are measured and a standard deviation thereof is determined statistically so that, when cigarettes are to be produced, they may have an aimed weight provided by a minimum allowable weight as accepted products added by an amount proportional to a variation of weight of content tobacco of cigarettes so as to yield little rejected cigarettes.
In other words, reduction of variations of weight of content tobacco of cigarettes will be attained by reduction of the aimed value of weight. This is the very reason why cigarette producers make great efforts to reduce variations of weight of content tobacco of cigarettes.
While it is important to maintain cigarette making machines sufficiently to try to reduce plays thereof arising from abrasion in order to reduce variations of amounts of content tobacco of cigarettes, the best solution is to provide a cigarette making machine additionally with a content tobacco amount controlling device of high performance. To this end, various systems have been proposed and put into practical use so far.
One of such systems is disclosed in Japanese Pat. Appln. Pub. No. 38-18750. This system makes use of the fact that there is some correlation between a weight of shredded tobacco and air permeability to control an amount of content tobacco using the air permeability as an index. This system, however, was not able to reduce deviations of amounts of content tobacco of cigarettes very much since it is influenced from a fluctuation of pressure at a sucking source and a grain size and composition of shredded tobacco so that the correlation between the weight of shredded tobacco and the permeability.
Another one of the systems is disclosed in U.S. Pat. Nos. 2,937,280 and 2,861,683. This system makes use of the fact that there is some correlation between an amount of shredded tobacco and the electrostatic capacity and uses the electrostatic capacity as an index. However, since this system is apt to be influenced from the water or temperature of shredded tobacco to disturb the correlation between the weight of shredded tobacco and the electrostatic capacity, it is not effective to reduce variations of amounts of content tobacco of cigarettes. Accordingly, this system is hardly put into practical use.
A further one of the systems makes use of the fact that there is some correlation between radio rays, particularly beta rays emitted from strontium 90, and the density of shredded tobacco to control the amount of shredded tobacco using the permeability of shredded tobacco to the radio rays. Since this system handles radio rays, it involves a problem of assuring the safety and another problem of a drift and responsiveness of an amplifier at a latter stage arising from the fact that an electric current outputted from an ion box which forms a detecting means is very weak. However, since a very good correlation exists between the permeability to radio rays and the density of shredded tobacco, this system is employed in almost all of cigarette making machines at present to detect an amount of content tobacco.
Meanwhile, Japanese Publication Patent No. 39-9450 discloses a system which includes a radio ray detector to provide a signal for controlling an amount of content tobacco of a cigarette to be produced by a cigarette making machine. However, since this system is designed to obtain a desired amount of content tobacco by controlling the speed of a feeder for shredded tobacco, the entire system becomes large-scaled and the responsiveness becomes low. Accordingly, the system has been seldom put into practical use.
A device which employs a radio ray detector to control an amount of content tobacco of a cigarette is also disclosed in Japanese Publication Patent No. 36-16250. In this system, the speed of a conveyor for shredded tobacco is regulated to obtain a desired amount of content tobacco and is thus superior to the system which is designed to regulate the speed of an entire feeder. However, this system is also inferior in the responsiveness and hence has not been put into practical use as yet.
Japanese Pat. Appln. Pub. No. 39-15949 discloses a different system which involves control utilizing air permeability and control using a radio ray density detector. In this system, a signal provided from the radio ray density detector is processed to move a trimmer up and down to vary an amount of content tobacco to be contained in a cigarette. Since responsiveness of this system is thus very quick comparing with the systems disclosed in Japanese Pat. Appln. Pub. No. 39-9450 and No. 36-15250 described above, this system is employed in almost all of cigarette making machines at present.
An example of the system in which a trimmer is moved up and down by means of a motor will be described below with reference to FIGS. 1 to 3.
Referring first to FIG. 1 is a perspective view showing a general construction of a cigarette making machine, shredded tobacco is attracted into and moved up within a chimney 10 and is then attracted into a layer on a bottom face of a perforated cigarette conveyor located at the bottom of a suction chamber 12. The shredded tobacco thus layered is carried in a leftward direction in FIG. 1 and is adjusted into a layer of a suitable thickness by means of a trimming device 14. The shredded tobacco of the adjusted layer thickness is transferred onto wrapping paper 18 placed on a cloth tape 16 and is wrapped into the wrapping paper 18 here. The wrapping paper 18 in which the shredded tobacco is wrapped is pasted by means of a pasting device 20 and is dried into a bar-like cigarette by a heater 22. Reference numeral 18' designates a wrapping paper supply roll.
The bar-like cigarette thus formed is passed through a radio ray density detector 24 to measure the density of content tobacco and is then cut into separate cigarettes by a cutter 26. The separately cut cigarettes are transferred onto and transported by a conveyor 28, and during such transportation, rejected products are removed by a magnet valve 30 to allow only accepted products to be loaded onto a tray 32.
Referring now to FIG. 2 which illustrates an example of the trimming device, a trimming disk 40 is secured to an end of a shaft 42 so that it may be rotated by way of a gear 44 mounted on the other end of the shaft 42. The trimming disk 40 is vertically positioned by a link 46 which is in turn positioned by moving either one of fulcra 48 and 50. A nut 52 is secured at the fulcrum 50, and a threaded portion of a rotary shaft 56 of a motor 54 is screwed in the nut 52. The motor 54 can rotate in opposite directions, and as the motor 54 is rotated in a forward or reverse direction, the link 46 is moved up or down relative to the fulcrum 48 to move up or down the disk 40. A thickness of a layer of shredded tobacco which passes this station is varied in response to up or down movement of the disk 40.
Referring to FIG. 3 which illustrates a circuit for driving the motor 54 to rotate alternatively in the forward or reverse direction, radio rays emitted from a radio ray source 60, for example, beta rays emitted from strontium 90, pass through a bar-like cirgarette 62 and are thrown into an ion box 64. If the density of content tobacco of the cigarette 62 is then high, the number of radio rays received by the ion box is reduced so that an ionization current produced by the ion box 64 is reduced. Meanwhile, radio rays emitted from another radio ray source 66 are passed through a standard density body 68 and is thrown into another ion box 70 which thus produces a standard ionization current.
Normally, positive and negative voltages are applied to the ion boxes 64 and 70, respectively, as seen in FIG. 3, and hence ionization currents of opposite polarity are generated at the ion boxes 64 and 70. Accordingly, if the density of content tobacco of a bar-like cigarette 62 to be measured is equal to that of a standard one, an output of an amplifier 72 is zero. Meanwhile, if the density of the bar-like cigarette 62 is higher than the standard density, an ionization current produced at the ion box 64 is lower in an absolute value than an ionization current produced at the ion box 70, and hence an electric current flows through a high resistor 74 so that the amplifier 72 provides a negative output therefrom. On the contrary, if the density of the bar-like cigarette 62 is lower than the standard density, the amplifier provides a positive output.
An averaging circuit 76 for averaging the output of the amplifier 72 includes an amplifier 76a and a negative feedback circuit therefore including a resistor 76c and a capacitor 76b connected in parallel to the resistor 76c.
Motor driving circuits 78 and 80 are connected to the motor 54, and when a signal averaged by the averaging circuit 76 is lower than a predetermined level, the driving circuit 78 drives the motor 54 to rotate in a direction to lower the disk 40 so as to raise the density of the bar-like cigarette 62, and on the contrary when the density is higher and the averaged signal is lower than another predetermined level, the driving circuit 80 drives the motor 54 to rotate in a direction to lift the disk 40 so as to lower the density of the bar-like cigarette 40. In this way, the density of bar-like cigarettes is adjusted to be maintained constant. Each of the motor driving circuits 78 and 80 includes a comparator 78a or 80a and a driver transistor 78b or 80b.
More particularly, upward or downward movement of the trimmer disk 40 is attained by forward or reverse rotation of the motor 54 in response to a result of determination whether an average in density over the length of a bar-like cigarette corresponding up to 50 cut cigarettes is higher or lower than a desired or aimed value. Accordingly, a desired responding speed cannot always be attained by the system.
In consideration of such circumstances, a new controlling device which further improves the controlling performance is proposed in Japanese Patent Application Publication No. 51-95198.
The proposed controlling device includes a means for irradiating radio rays onto tobacco feed into a cigarette making machine and for measuring an amount of radio rays passing through the tobacco to detect a density of the tobacco and convert the same into a corresponding electric signal, trimming means including a trimming disk for removing an excessive amount of shredded tobacco fed on a conveyor belt to adjust a cross sectional size of content tobacco, a piston means operated to move back and forth by pressure fluid from a pressure fluid distributor for moving the trimming disk up and down, and an electric hydraulic servo mechanism responsive to an electric signal from the means for outputting an electric signal proportional to an amount of radio rays passing through tobacco for operating the liquid pressure distributor, the electric signal having a negative feedback thereto of a vertical displacement of the trimming disk via a differential transformer. The proposed controlling device is improved particularly in the responding speed comparing with a device of the type including a motor to effect required controlling as described above.
Concretely, a ratio between a deviation of an average amount of content tobacco of cigarettes when controlled and a deviation of an average amount of content tobacco of cigarettes when not controlled, which ratio is regarded as an aim of an amount controlling performance, is 1/1.5 with the device using a motor while it is 1/4 with the last described device, providing particular improvement in the performance. Thus, it has been made sure that when the last described device is applied to a cigarette making machine having a capacity to produce 4,000 to 5,000 cigarettes per minute, higher effects than those attained by a controlling device of the type wherein a trimming disk is moved up and down by a motor where it is installed for a cigarette making machine having a capacity to produce 2,000 cigarettes per minute can be attained. Accordingly, the last described device is widely put into practical use.
However, where a cigarette making machine has a capacity to produce 8,000 cigarettes per minute, a content tobacco amount controlling device having quicker responsiveness is required.
Accordingly, the last mentioned Japanese laid-open patent application further proposes a device comprising trimming means including a trimming disk for removing an excessive amount of shredded tobacco fed on a conveyor band to adjust a cross sectional size of content tobacco, compressing means located adjacent the trimming disk for compressing shredded tobacco fed thereto against the conveyor band to remove a gap between the shredded tobacco and the conveyor band, means for irradiating radio rays to a portion of the shredded tobacco positioned between the compressing means and the conveyor band and for measuring an amount of radio rays passing through the tobacco to detect the density of the shredded tobacco and convert the same into a corresponding electric signal, a piston means operated to move back and forth by pressure liquid from a pressure liquid distributor for moving the trimming disk up and down, and an electric hydraulic servo mechanism responsive to an electric signal from the means for outputting an electric signal proportional to an amount of radio rays passing through tobacco for operating the liquid pressure distributor, the electric signal having a negative feedback thereto of a vertical displacement of the trimming disk via a differential transformer. It is confirmed that, with this device, the aforementioned ratio is about 1/8, proving an extremely high performance.
The device of the proposal has a few drawbacks, too. In particular, if the radio ray density detector is installed in the neighborhood of a trimming device 14 (FIG. 1) in order to effect controlling of an amount of content tobacco of cigarettes, a slight difference appears between a signal from the density detector and another signal from a radio ray density detector 24 (FIG. 1) for measuring after cigarette rods are formed. Normally, the difference is 0.5 to 1% or so, but it cannot be ignored at present days in which management of content tobacco of higher accuracy is required.
A reason why such a difference appears is that a signal obtained by measurement by the radio ray density detector before cigarette rods are formed contains a component caused by an amount of shredded tobacco which has passed out of holes of a perforated cigarette conveyor on the bottom of a suction chamber 12 (FIG. 1) before the shredded tobacco is wrapped into wrapping paper after the measurement by the radio ray density detector, and such an amount of shredded tobacco escaped causes a difference of the density when measured after cigarette rods are formed.
Accordingly, it is apparent that a most desirable content tobacco amount controlling device is such that a responding speed of control is the same as that in a device wherein a radio ray density detector is located directly behind a trimming disk while an aimed value of control is associated with a measured value by a radio ray density detector after cigarette rods are formed.